AN ARRANGEMENT OF THE FAMILIES AND THE 

 HIGHER GROUPS OF BIRDS. 



W. SHUFELI 



Birds constitute a class of the phylum Vertebrata, and 

 belong to the branch Craniata. Above the latter subphylum 

 they are associated with the Reptilia in the tribe Sauroj^sida, 

 which last in time has divided into two now distinct classes, 

 namely, Reptilia and Aves (see A Classification of Birds, postva). 

 Of all the existing vertebrate groups, birds are, morphologically 

 speaking, the most homogeneous ; probably none of the phyla 

 recognized by zoologists are more so. There is a very con- 

 siderable gap between a thrush and an ostrich, but it in no way 

 compares, ui the matter of profundit)-, with the gap that stands 

 between man and the duckbill, or between an elephant tortorse 

 and a garter snake. This morphological homogeneity in birds by 

 no means renders their taxonomy any the less difficult for us ; 

 indeed, for very obvious reasons it greatly tends to enhance the 

 intricacies of the problem. This fact is now so generally appre- 

 ciated by avian classifiers that it is quite needless to discuss it 

 in the present connection. 



To classify birds correctly and to point out the natural rela- 

 tionships and interrelationships of all the species and subspecies 



employ data of widely different nature. In the field of pahion- 

 tology we meet with a mass of material, the comparative study 

 of which has led to the conviction that Aves imd Reptilia ha\ e 

 arisen from a common stock. The indications of this have 1)\ 

 no means died out in certain existing representatives of these 

 two classes of the Sauropsida. For example, it is quite appar- 

 ent when we come to trace the ancestry of the existmg ostrich 

 and its surviving allies in various quarters of the globe. The 

 trend backward in time is distinctly reptile-wards and eventually 

 brings one to the consideration of a long-extinct assemblage of 

 833 



